I am going to utilize the First Year Choice for myself and my spouse in the month of June 2008, when I will meet the SPT.
By April 15th, I have to file 4868 for extension and "any" due taxes? My question is, how do I determine the "due" taxes before Apr 15th? Can I use form 1040 and online tools like TurboTax with option Married Filing Jointly for the whole year 2007? In that case, I have NO taxes due but a huge refund. So, should I take that amount for my filing before April 15th?

Please let me know.
Thanks.

If you determine that you are due a refund using TurboTax, then file Form 4868 with NO tax due.